How to make small objects emit a ton of light?
Mesh lights can be useful but they are quite an inefficient way to light your scene - especially with a large number of small lights as in your case. A better solution is to use Point Lamps to light the scene - although those are not visible to the camera which is not the effect you are looking for.

The solution is to use a Point Lamp embedded in the center of what would normally be your mesh lamp. This way the scene is lit by the Point Lamp (and can take advantage of all the optimisations in the renderer for handling point lamps) while the mesh lamp is still visible to the camera - but is set up to not block light from the lamp.

You can achieve this using the following material :



The Is Camera Ray light path input is used to switch between a Transparent shader and an Emission shader depending on whether visible to the camera. This means that for illuminating the scene the mesh will be invisible (so the lamp is visible) but in the actual render the mesh will emit light as if it were lighting the scene (so any effects in compositing (such as a Fog Glow) will still take account of the brightness).

As a comparison, here is a scene using a mesh lamp with 20 samples. The lamp on the right is a Point Lamp (and so is not visible) while the one on the left is a mesh lamp and so if visible to the camera. Note how the mesh lamp is very poor quality. Many more samples would be required to get acceptable results.



Using the above material produces the following result. Note how the mesh lamp is still visible but that the Point Lamp (positioned inside the mesh and set with a similar size as the mesh) is providing the actual illumination. Again, this is with only 20 render samples but the result is much more pleasing than the mesh lamp.